1. Field of the Invention
This invention relates to methods of making a thick microstructural oxide layer and devices utilizing same.
2. Background Art
SiO2 is a very desirable MEMS material, because of its low thermal conductivity, low thermal expansion coefficient, and good mechanical strength. Thick (10-100 μm) SiO2 layers have a variety of applications for thermal isolation in emerging high-temperature systems, for mechanical support of suspend elements in RFMEMS, and for micropackaging. Limited by diffusion/deposition rate, it is not feasible to produce thick SiO2 using standard high-temperature oxidation or deposition.
V. Lehmann, “Porous silicon-a new material for MEMS,” MEMS '96, pp. 106, describes one approach to fabricating thick SiO2 involving converting a portion of a silicon substrate to porous silicon by anodization, and then oxidizing the porous silicon to create a thick SiO2 layer of thickness ˜25 μm, as described by C. Nam, Y.-S. Kwon in their paper “Selective oxidized porous silicon (SOPS) substrate for microwave power chip-packaging,” Electrical Performance of Electronic Packaging, IEEE 5th Topical Meeting, 1996, pp. 202-204; and Ou Haiyan, Yang Qinqing, Lei Hongbing, Wang Hongjie, Wang Qiming, Hu Xiongwei in their paper “Thick SiO2 layer produced by anodisation,” Electronics Letters, V35, 1999, pp. 1950-1951.